1. Field of the Invention
The present invention relates to an identical object determination method and apparatus for determining whether or not objects detected by a plurality of sensors are identical and a displacement correction method and apparatus for correcting relative displacement of identical objects.
2. Description of the Related Art
In recent years, a monitoring system for recognizing a situation in one area or monitoring the situation in the area based on the recognition result has received attention and has become commercially practical in various applications of vehicle outside monitoring, railroad crossing monitoring, topographic recognition, an altimeter, etc. In this kind of monitoring system, to detect an object existing in an area, various sensors of a sensor using stereoscopic image processing for calculating the parallax of the object based on a pair of picked-up images, a laser radar, a millimeter wave radar, etc., are used. To execute recognition with high accuracy, using the sensors in combination is more advantageous than using the sensors singly. To use the sensors in combination, the sensors perform detection operation independently and thus it is necessary to determine whether or not the objects detected by the sensors are identical.
For example, JP-A-2000-131432 discloses a technique of using a millimeter wave radar and a laser radar in combination as sensors and determining whether or not the objects (obstacles) detected by the sensors are identical. In this related art, an obstacle detected by the millimeter wave radar and an obstacle detected by the laser radar in a determination area set surrounding that obstacle are determined identical.
JP-A-11-44756 and JP-A-09-218265 discloses attachment angle correction methods of a laser sensor and a camera. According to these methods, assuming that the objects detected by the sensors are identical, an attachment error of the sensors is corrected from the difference between the measurement values of the sensors. JP-A-6-230115 discloses a correction method of the distance measurement values of a laser sensor and a camera. According to this method, assuming that the objects detected by the laser sensor and the camera are identical, the distance measurement values are corrected from the difference between the distance measurement values provided by the laser sensor and the camera.
However, in the related art described in JP-A-2000-131432, a positional comparison between the objects detected by both the sensors is only made and therefore there is a possibility that the identical object will be determined two different objects (or two different objects will be determined the identical object). For example, in vehicle outside monitoring for monitoring the running circumstances ahead of the own vehicle, if an object running ahead of the own vehicle (preceding vehicle) and an object running in the opposite direction (oncoming vehicle) approach positionally, the objects maybe determined identical.
In the related arts concerning an error correction, basically an error correction is made assuming that the objects detected by the sensors are identical. However, in the related arts, if an error occurs to such an extent to which the objects detected by the sensors cannot be determined identical, the error cannot be corrected. Unless whether or not the objects detected by the sensors are identical is determined, the reliability of the error correction is not ensured.